Microwave tube



Sept. 16, 1952 M. RUDERFER 2,611,104

MICROWAVE TUBE Filed Oct. 21. 1949 fl/flemv 30525612,

I N V EN TOR.

. imam? Patented Sept. 16, 1952 UNITED STATES PATENT v v rnonowAvc rims Mar in Butler-fer, Br k yn Y... Application oetoberei, 1949, Serial No. 122.6 4 i 3C aim (01. 31's namely, those of low powerand continuous output which have proven ihefficientandthose of high power and intermittent or pulsed output, which have proven to be reasonably .emcient. The high power microwave apparatus operating at high voltages as the Magnetron, require the use of comparatively large magnets' and specially designed pulsing means, all of which auxiliary equipment is expensive and .spaceconsuming.

It is therefore another object of this-invention to provide a microwave tube which combines the advantages of previous types without the disadvantages, of novel, simple and cheap construction, capable of high power at good efii'ciency in continuous or intermittent duty; said devices being controlled directly by low voltage circuits, and easily pulsed by using simple and readily available means having standard components, thus eliminating all expensive and large auxiliary apparatus heretofore required for high power tubes.

Another object of this invention is to-provide a novel and improved electron discharge device of the class set forth, which permits a variation of frequency of oscillation over a wide range.

A further objecthereoi, is to provide a high power microwave oscillator which'does not depend upon secondary emission-from a cathode surface for its operation; thus affording fllonger life to the device.

Other objects and advantages will'becon e apparent as this disclosure proceeds.

In the accompanying drawings forming part of this specification, similar characters of reference indicate corresponding parts in all the views.

Fig. 1 shows an embodiment of my present invention, consisting essentially ,of an electron source and a cavity resonator. I'heembodiment illustrated is based upon standard tube construction. The circuit diagram included in this view, indicates the device used as an oscillator.

F g. 2 is a p rs ec v view. p rtlyin s ction, of the cavity resonator included in theIembodimentillustrated in Fig. I I

Fig, 3 shows an odified embodiment of this invention based upon standard construction.

Fig. 4 is an ,enlar ged sectional view taken at lines 4-.-.-4 in 3; The circuit diagram included herein, indicates the device used as an amplifier I Y -5 .1mm anot e mcd fled form @f eso at r discussed herein.

In the drawings, the numeral j d designates generally a cavity resonator positioned within h v c um, 9 1 9? Q FQYQW Thi e e o e. made of class 1; ethe s terial, also h use an e e r n ys which may e t wnvsntiena eleci heu d a rammat ll how an d ted Eth ll b th hume al 11, comp i ing a hea n l me lit-a cathode K nd a ont o and 28 The ca it reson .5a ho l w dy ha n a vpair o de osi s spac d central We p r eh One c th s a P rt o s s per t d e Ser as the screengrid 2|, which may .alsobe a grid of wires or othersuitable structure known in the art. The secondwall portion serves as a plate 22, The remainder of the bcdy of the re on t r m be (i -th n me she ti g to form the h l ws o W athere h sha e re er ed to as the avit e 3 and I de i d a and bott walls 25 ahdZB whic m e 9.! inu at e ma erial. ma e; a de o term th st uctur n a ho o asin hich'iqrm i u d m ractical an eff cient a Jeep 2 may bet ched in e d n one o 0t o sa d ca ities, throu h a bus :28 9 ih lileii mate ial, heinsijde end .of t, cop b ing in electrical contact with thecavity Wall. A common l ad for the sc e n :22! and the ;=n at 22, m y b connected along the centerof said plate as; show at 29. The cavity resonator 1-5, is so positioned in the envelope Zl6,-that the screenil is between the electron gun H and the plate '22.

iItmay sometimesbe desirableto connect the screen grid 2| and plate 22 directly, thus eliminating the side cavities and affordingthe minimum cavity volume, by side walls. ihere'sulting' cavity is therefore rectangular section,

two opposite sides of therectanglej being" the.

screen vlZiandplate i 22. I.

The cavity resonator and its manner of {a soc -c i n wit c-th electron un. may ah reh any res a d rm in the embodi ent l rated Fi s '3 d a the cavity SQ-1 3W tiis ahalow body having the incidents of structure as aforementioned to form the grid 2 l and the plate 22', and whose cavity 23'. is a perimetral race, and hence a continuous cavity completely surrounding said grid and plate. The perimetral cavity may be other than circular, and the cross sectional shapes of the various cavities illustrated may be other than circular.

The glass envelope l6 housing the electron gun I1, may also house the cavity resonator l, or else as shown, the envelope may be a shell having said resonator mounted thereon so that the scren grid 2 I is across its mouth. The loop 21 is positioned, inserted into cavity 23', through the insulative bushing 28'; the inside end of the loop being in electrical contact with the cavity wall. A common lead for the grid 2| and plate 22, may be at the center of the plate as at 29'. When the screen grid 2| i mounted across the mouth of the envelope, it is preferable to locate the common lead at the junction of screen grid 2 I and envelope It, in which case the envelope may be of conductive material and may serve as the aforementioned common lead.

Operation of the devices described, depends upon the secondary emission of electrons from the surface of the plate facing the grid. To facilitate this, it is desirable to coat such surface of the plate and even the surface of the screen grid facing the plate with one or more materials which aid the production of secondary electrons, as caesium oxide, barium oxide and other suitable materials known in the art.

Referring to the tube device shown in Fig. 1,

when the electron gun I! is operated, a stream of electrons emanating from the cathode I9, is initially accelerated towards the plate 22, by the positive potential applied to plate 22 and grid 2 I, by means of the battery 30. Some of these pri mary electrons are captured by the grid 2|, but

others travel through said grid and strike theplate 22. This causes the emission from said plate, of a number of secondary electrons, some of which are attracted to said plate 22 and some to the grid 2 I. For each primary electron, there are produced a large number of secondary electrons, so that the secondary electron flow from plate to screen and around the periphery of the conductors determining the cavities 23 and 24, to the battery 30, is greater than the primary electron flow from grid 2| to plate 22. Such secondary electron flow to the grid 21, momentarily causes the potential of said grid to decrease, and the potential of the plate 22 to increase, so that less secondary electrons are attracted to the grid 2!,

and more to the plate 22, thereby causing the secondary electron flow to decrease. This in turn produces a transient increase in potential of the grid 2|, and a corresponding decrease'of potential of the plate 22, so that the secondary electron fiow again increases. Thus a fluctuating current is created along the sides of the cavities 23 and 24; the frequency of oscillation being determined primarily by the resonant frequency of the cavities 23 and 24, and to a lesser degree by the spacing between the plate 22 and the grid 2 l, as well as by the velocity of the primary electrons from the gun H.

The current circulating along the sides of the cavities 23 and 24, produces an oscillating magnetic field in said cavities. Hence the'loop 27 is used to tap this oscillating energy for useful purposes, as for instance to an antenna 3! in which instance the device functions as an oscillator. Used in this manner as an oscillator, if the control grid is connected directly to the cathode,

continuous oscillations will result. For producing pulses of oscillation, the circuit shown in Fig. 1 may be used. The grid is connected to one side of the secondary of a transformer 34, and the other side of the secondary is connected to the negative terminal of battery 33. The positive terminal of battery 33 is connected to the cathode IS. The potential of battery 33 is such that the negative voltage on the control grid 20 normally prevents any flow of primary current from cathode to screen grid 2|. The primary of transformer 34 is connected in series with a battery 35 and a switch 36. Operation of the switch 36 causes a momentary positive pulse to be induced in the secondary of transformer 34 of sufficient magnitude that a flow of current for the duration of the pulse results from cathode to screen grid 2 thereby producing a pulse of oscillations.

The tube device of Fig. 4 of course operates in like manner when in the circuit shown in Fig, 1.

The frequency of oscillation, of'which the resonant frequency of the cavity is a factor, may be slightly varied by change of battery potential 30, or the voltage applied on the control grid 20 of the electron gun. When the exterior surface of the plate 22 is exposed as in Fig. 4, it i also possible to vary the frequency by moving the plate 22' to change its distance from the grid 2|, by suitable mechanical means as for instance an adjustment screw 40 engaged in a frame piece 4! which is fixed in relation to the device I 6. Any other suitable way to change the cavity shape, will accomplish the same result. In the embodiment shown, the conductor defining the cavity 23', in electrical connection with the plate 22' and the grid 2|, being. of thin metal, will be sufiiciently springy to urge return of said plate to normal unmoved position.

Referring to Fig. 4, one or more grids may be placed between the plate and screen grid. Such additional grid shown at 32, is connected for instance to a low amplitude ultra-high frequency source, as for instance an input signal at 31. This grid 32 will control the flow of secondary electrons from plate 22 to the grid 2|, and cause the output tapped by 21', to vary. in accordance with the low amplitude source 31. Thus the device will act as an amplifier. The tube device of Fig. 1, if provided with a grid akin to 32, between plate 22 and grid 2|, would of course operate in like manner when in the circuit shown in Fig. 4.

The present invention is capable of numerous forms and various applications without departing from the essential features herein disclosed. It is therefore intended and desired that the embodiments shown herein shall be deemed illustrative and not restrictive and that the patent shall cover all patentable novelty herein set forth; reference being had to the following claims rather than to the specific description herein to indicate the scope of this invention. 1

I claim: I Y

1. An envelope, means within said envelope to emit a stream of charged particles in a path in a given direction within the envelope, a plate positioned across the path of said stream, having the characteristic that it emits secondary electrons from its surface facing said means; such surface of the plate being of a material which aids such emission, a grid positioned across said path between said means and the plateand spaced from said plate, electrically continuous walls at least in part electrically conductive, electrically connecting the plate and grid and forming therewith an unobstructed cavity resonator in extension of, communicative with and including the space between said grid and plate and means carried by the envelope to conduct electromagnetic energy occurring within said cavity resonator, to a point exterior the cavity resonator.

2. An envelope, means within said envelope to emit a stream of charged particles in a path in a given direction within the envelope, a plate positioned across the path of said stream, having the characteristic that it emits secondary electrons from its surface facing said means; such surface of the plate being of a material which aids such emission, a grid positioned across said path between said means and the plate and spaced from said plate; the surface of the grid being of a secondary emissive material which aids emis-- sion from the grid, walls at least in part electrically conductive, electrically connecting the plate and grid and forming therewith an unobstructed cavity resonator in extension of, com municative with and including the space between said grid and plate and means carried by the envelope to conduct electro-magnetic energy occurring Within said cavity resonator toa point exterior the cavity resonator.

6 3. A device as defined in claim 1, wherein the cavity resonator is part of the envelope, the grid partitions the envelope and the entire envelope is of electrically conductive material whereby any part thereof may serve as thelead to grid and 9 plate.

MARTIN RUDERFER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,269,456 Hansen et al Jan. 13, 1942 2,272,605 Heising Feb. 10, 1942 2,392,379 Hansen Jan. 8, 1946 2,394,397 Mouromtsefi et al. Feb. 5, 1946 2,428,037 Roberts Sept. 30, 1947 2,466,063 Varian Apr. 5, 1949 2,498,461 Skellett Feb. 21, 1950 2,517,726 Skellett Aug. 8, 1950 

